Excitation-driven non-thermal conversion of few-layer graphenes into sp(3)-bonded carbon nanofilms

Abstract

The microscopic effect of electronic excitations on the transformation of few-layer graphene into sp(3)-bonded carbon nanofilm is examined through static and real-time propagation time-dependent density-functional theory. Statically, the presence of holes in high-lying valence bands is shown to reduce the energy barrier substantially. Dynamics of excited state electrons combined with Ehrenfest atomic motions reveals that non-thermal fast transformation from sp(2) to sp(3) can happen within a few hundreds femtoseconds. We suggest that once the efficient path of sp(3) carbon surface passivation is provided, the excitation from pi to pi* bands of few-layer graphenes can be utilized to achieve the transformation into nanoscale sp(3)-bonded carbon film without heating process.